Road World Championships
Date: 23-28 September Coverage: Live on BBC Red Button and BBC Sport website; highlights on BBC2
Thomas will be riding in two events in Italy ahead of the Worlds
Olympic gold medallist Geraint Thomas has replaced Mark Cavendish in the GB men's cycling team for the 2008 Road World Championships in Italy.
Four-time Tour de France stage winner Cavendish pulled out on Wednesday, citing fatigue for his withdrawal.
"I'm definitely looking forward to it," said Thomas ahead of the 23 September start. "It's my first senior Worlds."
Olympic gold medallist Nicole Cooke and silver medallist Emma Pooley ride in the GB women's team.
Thomas won the track team pursuit title in Beijing, and had been on the long list for the Road Worlds squad.
However, his form in the recent Tour of Britain - where he finished in 73rd place, 37 minutes behind the winner - suggested he might miss out on a place in Italy.
But the 22-year-old's experience of completing a Tour de France and a Giro d'Italia as a domestique, or support rider, in the Barloworld team counted in his favour.
"I'm there to help Steve [Cummings] and Dave [Millar]," said Thomas. "Whoever's the leader, I'm going to make sure I stay around them, and help them whenever they need me to get bottles or go back to the car."
"They're both going really well at the moment, so we'll be talking to each other and see how the race pans out on the day."
Cavendish was named in the men's squad on Wednesday, but withdrew almost immediately, calling an end to his season.
"I am tired. I am really beat," Cavendish recently told CyclingWeekly.co.uk.
"I know I won three stages in Missouri but I've got nothing left in the tank. I've been racing full-on since February and the Worlds isn't a race you can just turn up to and get round," he said.
"It's got nothing to do with the course. If I was on form I think I'd have the best chance of anyone in the team to do something, but I am not on form.
"I've had the journey back from Missouri, which has also really taken it out of me. It's the best thing to let someone else take the place."
The men's team is Thomas, Millar, Cummings, Chris Froome, Russell Downing and Ian Stannard.
Millar and Cummings also ride in the men's time-trial.
Cooke meanwhile, a four-time world junior champion, will be hoping to add the elite version to her honours for the first time in her career.
Along with Olympic time-trial silver medallist Pooley, the 25-year-old from Wales will be joined in the road-race team by Olympic team-mate Sharon Laws, and by Lizzie Armitstead and Jess Allen.
Laws and Pooley will also compete in the women's time-trial.
Elite men: David Millar, Chris Froome, Steve Cummings, Russell Downing and Ian Stannard plus one other.
Under-23 men: Ben Swift, Peter Kennaugh, Alex Dowsett, Jonny Bellis, Jonny McEvoy.
Elite women: Nicole Cooke, Emma Pooley, Sharon Laws, Jessica Allen and Lizzie Armitstead.
Elite men: Steve Cummings, David Millar.
Under-23 men: Alex Dowsett, Russell Hampton
Elite women: Emma Pooley, Sharon Laws, Nicole Cooke
Tuesday 23 September - Under-23 men's time trial
Wednesday 24 September - Elite women's time trial
Thursday 25 September - Elite men's time trial
Friday 26 September - Under-23 men's road race
Saturday 27 September - Elite women's road race
Sunday 28 September - Elite men's road race